The invention relates to a pneumatically or electromechanically actuable disc brake. A disc brake of such type is known from DE 10 2008 036 765, which is not a prior publication.
To achieve a minimization of components, which is always demanded, it is proposed in DE 10 2008 036 765 that the wear adjusting device be arranged between the control spindles and that the adjusting device be operatively connected to the control spindles by way of in central drive input elements of the adjusting device with the interposition of a gearing. In this way, it is possible to dispense with a transmission for the synchronous displacement of the control spindles; in particular, it is possible for functional parts which take up installation space to be arranged outside the region of overlap of the brake lever in the brake caliper, whereas the drive input spindles are guided to the outside through the brake caliper.
In this way, the brake caliper is not only reduced in size from a spatial aspect but also reduced in weight, which likewise meets a set demand. This weight reduction also leads to a reduction in fuel consumption of the vehicle, which constitutes a considerable advantage, both in economic terms and also with regard to a reduction in environmental pollution, over the disc brakes hitherto used.
Among other things, the adjusting device has a ball ramp coupling which, together with a ball cone coupling, forms a coupling that can be switched under load and by which an overload of the adjusting device during a braking process, that is to say when the brake lever is actuated, is prevented, such that the functional capability of the adjusting device is permanently ensured. With regard to the mode of operation of the adjusting device, reference is made to the cited DE 10 2008 036 765, which is not a prior publication.
To obtain fast response behavior of the ball ramp coupling, a torsion spring is provided. The torsion spring is connected at one side to a drive output disc, which engages into the drive input element of the adjusting device, and at the other side to a coupling ring. The drive output disc and coupling ring both are constituent parts of the ball ramp coupling.
Here, the torsion spring has hitherto been designed as a helical spring, that is to say is relatively large both in diameter and also in structural height.
The diameter of the torsion spring co-determines, inter alia, the size of installation openings in the brake caliper, the dimensions of which, in turn, have an influence on the stiffness of the brake caliper.
Since the brake caliper is a highly loaded component, minimizing the provision of openings is a constant aim in the design considerations during the configuration of a disc brake. In this respect, the known disc brake is in need of optimization.
It is an object of the invention to further develop a disc brake of the above-mentioned type such that its functional reliability is improved and its dimensioning is optimized.
This and other objects are achieved according to the invention, by a pneumatically or electromechanically actuable disc brake, in particular for a commercial vehicle, having: a brake caliper which engages over a brake disc; a brake application device, which is arranged in the brake caliper and which has a brake lever, for pressing brake pads against the brake disc; two control spindles which are arranged parallel to and spaced apart from one another and which can be moved axially by the brake application device; and an adjusting device which is positioned in the brake caliper and can be actuated by the brake lever and has a central drive input element and is arranged between the control spindles and is operatively connected to the control spindles via a gearing, with which adjusting device a wear-induced change in an air gap between the brake pad and the brake disc can be substantially compensated by an axial displacement of the control spindles. The central drive input element is connected to a drive input spindle via a ball ramp coupling, and the ball ramp coupling has a drive output disc, which engages into the drive input element, and a coupling ring to which in each case one end of a torsion spring is connected. The torsion spring is formed as a spiral spring.
The present invention advantageously uses a spiral spring as a torsion spring instead of a helical spring, wherein said spiral spring is preferably wound from a spring plate and has hooks or angled portions formed on the ends for fastening to the coupling ring, on the one hand, and to the drive output disc, on the other hand. Here, the drive output disc, which on the outside bears a slotted link toothing which corresponds to a gearing that actuates the control spindles, in effect forms a receptacle for the spiral spring, into which receptacle the coupling ring is recessed.
The spiral spring which is wound from spring plate is dimensioned in terms of its width so as to prevent the spiral spring from becoming jammed in a maximum gap formed between the coupling ring and the drive output disc. This gap arises during an actuation of the ball ramp coupling, during which, as a result of a relative rotation of the coupling ring with respect to the drive output disc, axial spreading between the two components takes place, such that the gap is formed.
It is, however, also contemplated in principle for the spiral spring to be produced from a spring wire, wherein the spiral spring has a significantly lower structural height than a helical spring hitherto used, in the same way as a spiral spring composed of wound spring plate. The low structural height permits a more compact structural height of the adjusting device.
The diameter of the spiral spring may, however, also be reduced in relation to that of a helical spring, in particular if, in the case of the design variant produced from spring plate, the individual windings bear directly against one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.